Encrypted optical communication system based on amplified spontaneous emission (ASE)

Abstract

The invention provides an encrypted optical communication system based on amplified spontaneous emission (ASE). The system integrates the broadband and high-noise characteristics of an ASE light source and a dynamic key mechanism. A wavelength division multiplexing technology is adopted, and devices such as a Mach-Zehnder modulator, a phase modulator and a polarization modulator are combined, so that effective modulation of data and key signals is realized. A dynamic secret key mechanism is introduced into the system, during each data transmission, an encrypted data signal is sent, and an encrypted secret key is synchronously transmitted to an authorized user, so that disposable use of the secret key is ensured, and the anti-cracking capability of the system is greatly improved. By means of the efficient mode that the secret key is transmitted and updated every time, the risk that the secret key is cracked by quantum computing for a long time can be effectively reduced, and the data confidentiality of the system is enhanced. In addition, the system further meets the requirement for flexible expandability, and a feasible research idea is provided for high-safety communication.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and more particularly to an encrypted optical communication system based on amplified spontaneous emission (ASE). The system aims to use ASE light as an optical carrier, and by virtue of its noise characteristics and wide bandwidth coverage, realize encryption and secret transmission of communication signals. The system is suitable for high-security communication scenarios, including military communications, government confidential communications, and other key areas that require countermeasures against eavesdropping. Background Art

[0002] With the acceleration of the global informatization process, information security issues have increasingly become the focus of attention from all walks of life. In optical fiber communication systems, it is crucial to ensure that data is not eavesdropped or tampered with during transmission. Currently, many communication systems rely on digital encryption algorithms (such as AES, RSA, etc.) to ensure data security. These encryption algorithms have strong security in theory, but with the improvement of computing power, especially the gradual development of quantum computers, traditional algorithms face increasingly severe cracking risks.

[0003] In modern fiber-optic communication systems, the continuous upgrading of eavesdropping methods has made it impossible for communication systems that rely solely on upper-layer encryption to provide sufficient security in certain specific scenarios. For example, military communications, government confidential communications, and confidential data transmission in the financial field not only need to resist attacks at the algorithm level, but also need to ensure the confidentiality of signals at the physical level to prevent the signals from being detected or extracted during transmission. Therefore, the security design of the physical layer cannot be ignored and has become an important supplementary means to combat eavesdropping.

[0004] In recent years, researchers at home and abroad have proposed many methods to improve the security of the physical layer of optical fiber communication. For example, chaotic laser communication, quantum noise stream cipher, optical code division multiple access (OCDMA), all-optical exclusive OR (XOR), optical frequency hopping, and optical covert communication. However, for chaotic laser communication, the design and implementation of the laser are relatively complex and require precise synchronization; quantum noise stream cipher requires the use of professional quantum communication equipment, which is costly; although optical code division multiple access technology is effective, its encoding and decoding process requires the support of complex algorithms, which undoubtedly increases the difficulty of technical implementation; optical frequency hopping technology is limited by the limited spectrum resources, and its development is subject to certain constraints. Optical covert communication has achieved the concealment of transmission signals to a certain extent, but in the absence of a strong encryption mechanism and efficient key management, its security still faces severe challenges. Therefore, there is still room for further improvement in the physical layer security of optical communication. Traditional optical communication systems widely use continuous wave lasers as carriers, but due to their concentrated frequency and strong predictability, they are easily detected by external devices. Relatively speaking, the wideband and high noise characteristics of the amplified spontaneous emission (ASE) light source can effectively hide the transmission signal, allowing it to absorb noise signals in eavesdropping devices, thereby greatly improving the concealment of communications. At the same time, combined with a specific encryption method, the encryption of the signal can be further enhanced at the physical level, making the system more secure in a complex eavesdropping environment. In response to the existing scheme of using ASE light source for phase encryption, this scheme proposes a key improvement: a dynamic key mechanism. That is, during each transmission, not only the encrypted data signal is sent, but the encrypted key is also transmitted to the authorized user, making the key a one-time key. This improvement greatly improves the system's anti-cracking ability, enhances the security and confidentiality of the key, and makes key management more flexible and efficient. By updating the key for each transmission, this scheme effectively reduces the risk of long-term keys being cracked by quantum computing and enhances the data confidentiality of the system. Summary of the invention

[0005] In order to improve the security and concealment of the communication system, the present invention provides an encrypted optical communication system based on amplified spontaneous emission (ASE), which can effectively enhance the security and concealment of the communication system and ensure the confidentiality and integrity of information.

[0006] In order to achieve the above-mentioned purpose, the present invention establishes a communication link based on wavelength division multiplexing, and the devices in the link include an amplified spontaneous emission light source, an arbitrary waveform generator, a variable optical power attenuator, a Mach-Zehnder modulator, a polarization modulator, a phase modulator, a polarization controller, a polarization beam splitter and a polarization beam combiner, a wavelength division multiplexer, an optical coupler, an optical amplifier, an optical filter, an optical fiber, a photodetector, a data recovery module and a bit error rate tester.

[0007] The process of an encrypted optical communication system based on amplified spontaneous emission (ASE) described in the present invention is as follows:

[0008] Step 1: The amplified spontaneous emission optical carriers output by the amplified spontaneous emission light source 1 and the amplified spontaneous emission light source 11 are injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 respectively after passing through the polarization controller 2 and the polarization controller 12.

[0009] Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal m(t) generated by the arbitrary waveform generator 3 ; the optical carrier of the polarization modulator 4 is modulated by the key signal v(t) generated by the arbitrary waveform generator 13 .

[0010] The signal output by the Mach-Zehnder modulator 14 is expressed as:

[0011]

[0012] Among them, E in (t) is the amplitude of the light field output by the amplified spontaneous radiation light source 11, m(t) is the data signal, β1 = πV0 / V π1 is the modulation index of the Mach-Zehnder modulator 14, V π1 is the half-wave voltage of the Mach-Zehnder modulator 14, V0 is the data signal amplitude, Fixed phase difference.

[0013] Mach-Zehnder modulator 14 operates at quadrature point Then (1) can be converted into:

[0014]

[0015] The signal output by the polarization modulator 4 is expressed as:

[0016]

[0017] Among them, E x (t), E y (t) is the light field in the orthogonal polarization state, E0(t) is the light field amplitude output by the amplified spontaneous emission light source 1, ω is the angular frequency of the light signal, v(t) is the key signal, v π2 is the half-wave voltage of the polarization modulator 4.

[0018] Step 3: The optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; the optical signal after passing through the polarization modulator 4 is divided into two branches by the polarization beam splitter 6.

[0019] The transfer function of dispersion 14 is expressed as:

[0020]

[0021] Wherein, ω0 is the central angular frequency of the optical signal, and β is the dispersion coefficient.

[0022] After dispersion 14, the output signal is expressed as:

[0023] E' out (t) = F -1 [F[E out (t)]·H D (ω)] (5)

[0024] Where F(·) is the Fourier transform, F -1 (·) is the inverse Fourier transform.

[0025] By adjusting the polarization controller 5, the two-way signal output by the polarization beam splitter 6 is expressed as:

[0026]

[0027] Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal; encrypt the two branch signals after the polarization beam splitter using optical filters respectively, and then combine them into one signal using the polarization beam combiner 9.

[0028] The output signal of the encrypted phase modulator 16 is expressed as:

[0029]

[0030] Wherein, v(t) is the driving signal of the phase modulator 16, i.e., the key signal, and v π3 is the half-wave voltage of the phase modulator 16

[0031] The two signals output by the filter are expressed as:

[0032] E BPF (t) = F -1 [F[E out1 (t)]·H BPF (ω)](9)

[0033] E BRF (t) = F -1 [F[E out2 (t)]·H BRF (ω)](10)

[0034] Among them, H BPF (ω) is the transfer function of the bandpass filter 7, H BRF (ω) is the transfer function of the band-stop filter 8.

[0035] The output signal of the polarization beam combiner 9 is expressed as:

[0036]

[0037] in, is the unit vector in the x direction, is the unit vector in the y direction.

[0038] Step 5: The signal after the phase modulator and the signal synthesized by the polarization combiner are synthesized into one signal by using the wavelength division multiplexer 17 and transmitted to the optical fiber 18.

[0039] Step 6: After the optical signal is transmitted through the optical fiber 18, the dispersion compensation optical fiber 19 is used to compensate for the dispersion, and the optical signal is sent to the demultiplexer 21 through the optical amplifier 20 to complete the complete reception of the optical signal, and then the key signal is decrypted by the filter. The photoelectric detector 23 is used to restore the electrical signal, and the data recovery module 24 is used to restore the key signal to its original state. The recovered key signal is then input into the phase modulator 26 to perform phase decryption on the data signal, and the introduced dispersion is compensated after phase decryption. The photoelectric detector 28 is used to restore the electrical signal, and the data recovery module 29 and the bit error rate test 30 are used to perform data recovery and bit error rate test on the data signal.

[0040] First, the key signal is filtered and the output signal is expressed as:

[0041] E k (t) = F -1 [F(E PC (t))·H BRF (ω)]=αE out2 (t)(12)

[0042] Where α is the optical fiber attenuation factor.

[0043] The filtered key signal is sent to the photodetector 23, and the generated key signal current is expressed as:

[0044]

[0045] in, is the responsivity of the photodetector 23, and v(t) is the recovered key signal.

[0046] The recovered key signal v(t) is injected into the decryption phase modulator 26, and the output signal is expressed as:

[0047]

[0048] The output signal of the decryption phase modulator is dispersed 27 times compensated, and the output signal is:

[0049]

[0050] Among them, H * D (ω) is H D (ω) Complex conjugate.

[0051] The dispersion compensated signal is sent to the photodetector 28, and the generated data signal current is expressed as:

[0052]

[0053] in, The responsivity data of the photodetector 28, m(t) is the recovered data signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Flow chart of an encrypted optical communication system based on amplified spontaneous emission (ASE) according to the present invention

[0055] Figure 2 A schematic diagram of an optical link of an encrypted optical communication system based on amplified spontaneous emission (ASE) proposed by the present invention;

[0056] Figure 3 It is the optical signal diagram and electrical signal diagram after the data signal is modulated, encrypted and decrypted;

[0057] Figure 4 It is the spectrum diagram of two-way signal after wavelength division multiplexing;

[0058] Figure 5 It is the electrical spectrum after wavelength division multiplexing of two signals;

[0059] Figure 6 It is the electrical time domain diagram after wavelength division multiplexing of two signals; DETAILED DESCRIPTION

[0060] The present invention will be further described below in conjunction with the accompanying drawings:

[0061] Figure 1 The flowchart of the encryption and secret communication system based on amplified spontaneous emission (ASE) of the present invention specifically includes the following steps:

[0062] Step 1: Figure 2 As shown, the amplified spontaneous emission optical carriers output by the amplified spontaneous emission light source 1 and the amplified spontaneous emission light source 11 are injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 respectively after passing through the polarization controller 2 and the polarization controller 12 .

[0063] Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal m(t) generated by the arbitrary waveform generator 3; the optical carrier of the polarization modulator 4 is modulated by the key signal v(t) generated by the arbitrary waveform generator 13. Figure 3 As shown, the signal is hidden in the noise.

[0064] The signal output by the Mach-Zehnder modulator 14 is expressed as:

[0065]

[0066] Among them, E in (t) is the amplitude of the light field output by the amplified spontaneous radiation light source 11, m(t) is the data signal, β1 = πV0 / V π is the modulation index of the Mach-Zehnder modulator 14, V π1 is the half-wave voltage of the Mach-Zehnder modulator 14, V0 is the data signal amplitude, Fixed phase difference.

[0067] Mach-Zehnder modulator 14 operates at quadrature point Then (1) can be converted into:

[0068]

[0069] The signal output by the polarization modulator 4 is expressed as:

[0070]

[0071] Among them, E x (t), E y (t) is the light field in the orthogonal polarization state, E0(t) is the light field amplitude output by the amplified spontaneous emission light source 1, ω is the angular frequency of the light signal, v(t) is the key signal, v π2 is the half-wave voltage of the polarization modulator 4.

[0072] Step 3: The optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; the optical signal after passing through the polarization modulator 4 is divided into two branches by the polarization beam splitter 6.

[0073] The transfer function of dispersion 14 is expressed as:

[0074]

[0075] Wherein, ω0 is the central angular frequency of the optical signal, and β is the dispersion coefficient.

[0076] After dispersion 14, the output signal is expressed as:

[0077] E' out (t) = F -1 [F[E out (t)]·H D (ω)] (5)

[0078] Where F(·) is the Fourier transform, F -1 (·) is the inverse Fourier transform.

[0079] By adjusting the polarization controller 5, the two-way signal output by the polarization beam splitter 6 is expressed as:

[0080]

[0081] Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal, such as Figure 3 As shown; the two branch signals after the polarization beam splitter are encrypted using optical filters respectively, and then the polarization beam combiner 9 is used to combine one signal.

[0082] The output signal of the encrypted phase modulator 16 is expressed as:

[0083]

[0084] Wherein, v(t) is the driving signal of the phase modulator 16, i.e., the key signal, and v π3 is the half-wave voltage of the phase modulator 16

[0085] The two signals output by the filter are expressed as:

[0086] E BPF (t) = F -1 [F[E out1 (t)]·H BPF (ω)](9)

[0087] E BRF (t) = F -1 [F[E out2 (t)]·H BRF (ω)](10)

[0088] Among them, H BPF (ω) is the transfer function of the bandpass filter 7, H BRF (ω) is the transfer function of the band-stop filter 8.

[0089] The output signal of the polarization beam combiner 9 is expressed as:

[0090]

[0091] in, is the unit vector in the x direction, is the unit vector in the y direction.

[0092] Step 5: Use wavelength division multiplexer 17 to combine the signal after the phase modulator and the signal combined by the polarization beam combiner into one signal and transmit it to optical fiber 18. Figure 4 , Figure 5, Figure 6 As shown in the figure, after wavelength division multiplexing, the signal and key are hidden in the optical and electrical domains.

[0093] Step 6: After the optical signal is transmitted through the optical fiber 18, it is dispersion compensated by the dispersion compensation optical fiber 19, and sent to the demultiplexer 21 through the optical amplifier 20 to complete the complete reception of the optical signal, and then the key signal is decrypted by the filter. The photodetector 23 restores it to an electrical signal, and the data recovery module 24 restores the key signal to its original state. The recovered key signal is then input into the phase modulator 26 to perform phase decryption on the data signal, such as Figure 3 , Figure 4 As shown, the introduced dispersion is compensated after phase decryption. The photoelectric detector 28 restores the data signal to an electrical signal, and the data recovery module 29 and the bit error rate test 30 are used to perform data recovery and bit error rate test on the data signal.

[0094] First, the key signal is filtered and the output signal is expressed as:

[0095] E k (t) = F -1 [F(E PC (t))·H BRF (ω)]=αE out2 (t)(12)

[0096] Where α is the optical fiber attenuation factor.

[0097] The filtered key signal is sent to the photodetector 23, and the generated key signal current is expressed as:

[0098]

[0099] in, is the responsivity of the photodetector 23, and v(t) is the recovered key signal.

[0100] The recovered key signal v(t) is injected into the decryption phase modulator 26, and the output signal is expressed as:

[0101]

[0102] The output signal of the decryption phase modulator is dispersed 27 times compensated, and the output signal is:

[0103]

[0104] Among them, H * D (ω) is H D (ω) Complex conjugate.

[0105] The dispersion compensated signal is sent to the photodetector 28, and the generated data signal current is expressed as:

[0106]

[0107] in, The responsivity data of the photodetector 28, m(t) is the recovered data signal.

[0108] In summary of the above description, the present invention exhibits the following features: 1). Simple and efficient structure: The present invention adopts a simple encrypted optical communication system that can support ultra-large capacity data transmission. By hiding the modulated signal in the optical and electrical domains, the secret transmission of information is achieved, which greatly reduces the possibility of information being detected and intercepted, thereby ensuring the high security of data transmission. 2). Dynamic key update mechanism: The present invention introduces dynamic key transmission technology. During each information transmission process, the system automatically updates the key and modulates and encrypts these keys. This strategy not only improves the security of data transmission, but also effectively reduces the risk of keys being illegally cracked, providing a strong guarantee for the confidential transmission of information.

Claims

1. An encrypted optical communication system based on amplified spontaneous emission (ASE), characterized in that: The following steps are involved: Step 1: The amplified spontaneous emission optical carriers output by the laser source 1 and the laser source 11 are respectively injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 after passing through the polarization controller 2 and the polarization controller 12; Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal generated by the arbitrary waveform generator 3; the optical carrier of the polarization modulator 4 is modulated by the key signal generated by the arbitrary waveform generator 13; Step 3: the optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; The optical signal after passing through the polarization modulator 4 is split into two branches by the polarization beam splitter 6; Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal; encrypt the two branch signals after the polarization beam splitter using optical filters respectively, and then combine them into one signal using the polarization beam combiner 9; Step 5: The signal after the phase modulator and the signal synthesized by the polarization combiner are synthesized into one signal by using the wavelength division multiplexer 17 and transmitted to the optical fiber 18; Step 6: After the optical signal is transmitted through the optical fiber 18, the dispersion compensation optical fiber 19 is used to compensate for the dispersion, and the optical signal is sent to the demultiplexer 21 through the optical amplifier 20 to complete the complete reception of the optical signal, and then the key signal is decrypted by the filter. The photoelectric detector 23 is used to restore the electrical signal, and the data recovery module 24 is used to restore the key signal to its original state. The recovered key signal is then input into the phase modulator 26 to perform phase decryption on the data signal, and the introduced dispersion is compensated after phase decryption. The photoelectric detector 28 is used to restore the electrical signal, and the data recovery module 29 and the bit error rate test 30 are used to perform data recovery and bit error rate test on the data signal.

2. The encrypted optical communication system based on amplified spontaneous emission (ASE) according to claim 1 is unique in that the system uses ASE light as a carrier to perform polarization modulation on the key signal. This modulation process ensures the security of the key signal, and then merges it with the encrypted data signal to form a single signal stream, which is efficiently transmitted through a single-mode optical fiber. At the receiving end, the key signal v(t) is first recovered, and then the recovered key signal is used to drive the phase modulator to perform a decryption operation on the data signal, thereby accurately restoring the original data signal m(t).

3. The encrypted optical communication system based on amplified spontaneous emission (ASE) according to claim 2, characterized in that: The system is designed with a high degree of dynamic security. Specifically, it implements an instant key update mechanism: each time information is transmitted, a new key is generated, modulated and encrypted, and then securely sent to the receiving end. This frequent key update strategy reduces the risk of illegal key cracking and provides a more solid protection barrier for information transmission.

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